This invention relates to food processing, and more particularly, to reducing microbe content in processed foodstuffs. The invention encompasses both an apparatus and a method for physically manipulating organic materials such as foodstuffs to reduce microbe content.
Foodstuffs are inevitably exposed to microbes in the course of processing or in the course of handling prior to processing. Microbes are part of the natural decay process of organic material and may be deposited on foodstuffs through the air or by contact between the foodstuff and contaminated equipment or other material. Although some microbes may be relatively benign, others contribute to spoilage and some can cause serious illness. Lactic acid producing bacteria are examples of benign microbes, while some strains of E. Coli, Salmonella, Listeria, and Staph bacteria are examples of pathogenic microbes which can cause serious illness when ingested by humans.
Even with careful processing practices, foodstuffs may be exposed to pathogenic microbes during processing or initial handling. Consumers may become ill by ingesting a foodstuff contaminated with pathogenic microbes. However, the risk of illness from dangerous microbes which may be present in foodstuffs is reduced by careful handling and cooking by the consumer. In larger cuts of meat for example, dangerous microbes may only be present on the surface of the meat and are readily killed in the cooking process.
Ground or chopped and mixed foodstuffs, including ground beef, may carry dangerous microbes which are killed only after thoroughly cooking the material. The reason for this is that dangerous microbes residing at the surface of a larger piece of the foodstuff may be distributed throughout the final ground or chopped product as the large piece is ground and mixed together with other pieces. Thorough cooking is required in order to kill microbes residing in the center of a piece of ground and mixed foodstuff.
It is generally desirable to control the growth of microbes and reduce microbe content in foodstuffs. Microbe content and growth in foodstuffs may be reduced by applying chemical additives or preservatives to the foodstuff. These chemical additives or preservatives, however, may not be acceptable to consumers, or may adversely affect the quality of the foodstuffs.
Alternatively to chemical additives or preservatives, heat may be used to kill microbes in foodstuffs. However, heat processing or sterilization often adversely affects the quality or characteristics of the foodstuff and may make the food product undesirable to the consumer.
It is an object of the invention to provide a method for reducing microbe content in foodstuffs and to provide an apparatus for performing the method.
The method of the invention comprises physically manipulating or applying stress to the foodstuff while the foodstuff is in a frozen state. While the mechanism by which the process reduces live microbe count is not fully understood, physical manipulation according to the invention has been shown to significantly reduce microbe content in the treated foodstuffs.
The process according to the invention may be performed as a continuous process or as a batch process. In either case, the foodstuff is cooled by a suitable freezing arrangement to a process temperature no greater than the freezing point of the foodstuff to place the foodstuff in a frozen state. As used in this disclosure and the accompanying claims, the xe2x80x9cfreezing point of the foodstuffxe2x80x9d means the temperature at which ice crystals begin to form in the foodstuff at a given pressure. In this xe2x80x9cfrozenxe2x80x9d state according to the invention, liquid material may still be present in the foodstuff along with the ice crystals which have formed. For process temperatures well below the freezing point of the foodstuff, very little or substantially no liquid material may be present in the foodstuff.
Once the foodstuff is frozen, a suitable manipulating arrangement is used to manipulate the frozen material while the material is in a temperature range comprising temperatures not greater than the freezing point of the foodstuff. This physical manipulation according to the invention produces relative movement in the foodstuff. In this sense, xe2x80x9crelative movementxe2x80x9d means movement between one point in the foodstuff and adjacent points in the foodstuff. It is believed that this relative movement, which preferably occurs throughout the volume of the frozen foodstuff, damages microbes which may be present in the foodstuff and effectively kills much of the live microbes. The invention encompasses manipulating the foodstuff two or more times at substantially the same process temperature or at different temperatures. For example, the foodstuff may be placed at the desired process temperature either from a higher temperature or after being frozen at a lower temperature, and then manipulated once using a suitable manipulating device. After this initial manipulation, the foodstuff may be manipulated again either at the same process temperature or at another process temperature and either with the same type of manipulating device or another type of device. Also, the manipulation steps may be widely spaced apart in time. For example, a comminuted meat product may be manipulated according to the invention one or more times in the production of the product, and may be manipulated again after shipment to another processor or user of the comminuted meat product.
Numerous manipulating arrangements may be employed within the scope of the invention as set out in the following claims. Generally, manipulating arrangements may be classified as (1) compression-type devices, (2) cutting-type devices, or (3) working-type devices. Compression-type manipulating devices include devices which compress the frozen foodstuffs into a block of material, screw-type compressors which compress the frozen foodstuffs as the material is conveyed along a conduit by an auger or screw mechanism, and rolling devices which compress the frozen material as it moves relative to one or more rollers. Cutting-type manipulating devices include grinders, choppers, and slicing devices. Working-type manipulating devices include arrangements which impact the frozen foodstuff and arrangements which bend, stretch, or otherwise work the frozen foodstuff. In each manipulating device, the device may define a working area within which frozen foodstuff is manipulated. As used in the following claims, and unless otherwise specified, a manipulating apparatus or device encompasses any of the types of manipulating devices described in this disclosure. Similarly, a manipulating step may be performed by any of the manipulating devices disclosed herein unless a particular manipulation arrangement is specified.
Regardless of the particular manipulating arrangement employed to manipulate the frozen foodstuffs according to the invention, a manipulator temperature control system associated with the manipulating arrangement preferably controls the temperature of the manipulating arrangement surfaces which come in contact with the frozen foodstuffs. The manipulator temperature control system may cool the surfaces of the manipulating arrangement to ensure that heat from the surfaces of the manipulating arrangement does not raise the temperature of the foodstuffs to a temperature above the desired process temperature. Alternatively, the manipulator temperature control system may heat the manipulating arrangement surfaces and thereby heat the frozen foodstuffs from a lower process temperature to the freezing temperature or even slightly above the freezing temperature. Also, maintaining the surfaces of the manipulating arrangement at a temperature near the process temperature or slightly above the process temperature helps prevent the foodstuffs from sticking to the manipulator surfaces.
One preferred implementation of the invention utilizes a pressure change in a frozen foodstuff to place the foodstuff in a fully or partially unfrozen state. The pressure may be applied as part of a manipulation of the foodstuff or as a separate step. In this aspect of the invention, the foodstuff at a process temperature is compressed by a suitable arrangement to place at least a portion of the foodstuff in a condition in which that portion of the material is not in a frozen state. When the pressure is released, the foodstuff once again goes to a frozen state with ice crystals forming very rapidly.
Physical manipulation according to the invention may be accompanied by manipulating the foodstuff pH before a physical manipulation or both before and after a physical manipulation. The pH of the foodstuff may be modified in any suitable manner. For example, a higher pH foodstuff such as lean finely textured beef may be mixed with a regular ground beef to modify the pH of the resulting mixture. The process of producing lean finely textured beef, which increases pH with respect to the starting material, also represents a suitable pH modifying step. Also, a foodstuff may be placed in contact with NH3 (Ammonia) in gaseous or aqueous form to increase the pH of the foodstuff. U.S. patent application Ser. No. 08/803,322, now U.S. Pat. No. 5,871,795, the disclosure of which is hereby incorporated herein by this reference, discloses a pH modifying apparatus and method which may be employed in this invention. pH modification within the scope of the invention also encompasses decreasing pH. The pH of a foodstuff may be decreased by placing the foodstuff in contact with a pH reducing material such as CO2, for example.
The present invention is applicable to many types of foodstuffs. For example, comminuted foodstuffs such as ground meats are ideally suited for the present process. The invention may also be applied to larger cuts of meat or cubed or sliced meats. Furthermore, the invention is applicable to vegetable and fruit material including juices. For purposes of this disclosure and the accompanying claims, xe2x80x9cfoodstuffxe2x80x9d may include substantially any food material or mixture of materials which can be held in a workable or manipulatable form at a process temperature. Also, the treatment process is applicable to other materials which contain water and are capable of supporting microbe growth. These other materials are to be considered equivalent to foodstuffs for the purposes of the following claims.
Commonly, the treatment process according to the invention includes forming the material to be treated into a workpiece or a plurality of workpieces either before or after being placed at a process temperature. The workpiece or workpieces may then be physically manipulated by the suitable manipulating device.
These and other objects, advantages, and features of the invention will be apparent from the following description of the preferred embodiments, considered along with the accompanying drawings.